Add default callback timesteps

[nefrathenrici]

Currently this fails due to missing callback kwargs containing callback timesteps:

julia> simulation = CA.AtmosSimulation{FT}()
ERROR: UndefKeywordError: keyword argument `dt_cloud_fraction` not assigned
Stacktrace:
 [1] default_model_callbacks(model::ClimaAtmos.AtmosModel{…}; kwargs::@Kwargs{…})
   @ ClimaAtmos ~/Downloads/ClimaAtmos.jl/src/callbacks/get_callbacks.jl:692
 [2] (ClimaAtmos.AtmosSimulation{…})(; model::ClimaAtmos.AtmosModel{…}, params::ClimaAtmos.Parameters.ClimaAtmosParameters{…}, context::ClimaComms.SingletonCommsContext{…}, grid::ClimaCore.Grids.ExtrudedFiniteDifferenceGrid{…}, initial_condition::ClimaAtmos.InitialConditions.DecayingProfile, dt::Int64, start_date::Dates.DateTime, t_start::Int64, t_end::Int64, ode_config::ClimaTimeSteppers.IMEXAlgorithm{…}, surface_setup::ClimaAtmos.SurfaceConditions.DefaultExchangeCoefficients, itime::Bool, job_id::String, output_dir::Nothing, output_dir_style::String, restart_file::Nothing, detect_restart_file::Bool, tracers::Vector{…}, default_callbacks::Bool, callbacks::Tuple{}, callback_kwargs::Tuple{}, default_diagnostics::Bool, diagnostics::Tuple{}, use_dense_jacobian::Bool, use_auto_jacobian::Bool, approximate_linear_solve_iters::Int64, auto_jacobian_padding_bands::Int64, debug_jacobian::Bool, checkpoint_frequency::Float64, log_to_file::Bool)
   @ ClimaAtmos ~/Downloads/ClimaAtmos.jl/src/simulation/AtmosSimulations.jl:221
 [3] (ClimaAtmos.AtmosSimulation{Float32})()
   @ ClimaAtmos ~/Downloads/ClimaAtmos.jl/src/simulation/AtmosSimulations.jl:127
 [4] top-level scope
   @ REPL[18]:1
 [5] top-level scope
   @ REPL:1
Some type information was truncated. Use `show(err)` to see complete types.

To get this working, the user needs to pass callback_kwargs = (; dt_cloud_fraction = "150secs", dt_rad = "600secs") into the AtmosSimulation call.